9. The lithosphere and the soil as power equipment and hazard Methods of soil study II.

1. Soil sampling The most commonly used sampling design for many field studies is systematic sampling using either transects or grids. Map of systematic soil sampling

Methods of soil sampling : 1.Sampling from soil profile 2.Sampling from soil profile 3.Untamed soil sample 4.Average sampling 5.Special soil sampling 6.Sampling of groundwater Sampling from soil profileSampling with hand soil core

2. Handling and storage of soil samples The requirements for each sampling campaign will differ, but a typical sequence is as follows: - Collect composite sample in the field or from the experimental system. - If the sample is too large, reduce clump size, mix and package a portion of the composite to transport to the laboratory. - Collect a subsample for determination of moisture content, the subsample is weighed, dried at 105°C, and reweighed. - Dry remaining sample to a moisture content suitable for further sample handling. - If appropriate and required, further reduce clump size, such as by grinding. - Subsample as required for analysis. - Prepare an archive sample.

3. Physical properties of soils Texture Sticky limit Hygroscopicity Density of the soil Bulk density of the soil Calculation of total porosity Determination of soil porosity Water retention Capillary action in soil

Texture Falling time of different size grains Grain size of soil according to the Atterberg system Particle-size distribution analysis is a measurement of the size distribution of individual particles in a soil sample. In the USDA classification system (Soil Survey Staff, 1953, 1993), soil texture refers to the relative proportions of clay, silt, and sand on a <2-mm basis. Namename of gains Diameter of grains (mm) Skeletonpebbles, blocks> 2,0 Fine soil coarse grained sand (Dh)2,0 - 0,2 fine grained sand (Fh)0,2 - 0,02 mud (I)0,02 - 0,002 clay (A)< 0,002 2r (mm) t w (°C) v (cm/s) time to falling 10 cm 0,02 density = 2,7 g/cm 3 153,30* h 05’03” 203,75* h 04’27” 254,20* h 03’58” 0, ,25* h 30’00” 203,67* h 35’00” 254,16* h 40’00”

Sticky limit Sticky limits are the limits of water content used to define soil behaviour. Soils can be classified to four groups on the base of their stickiness: Determination of Sticky limit

Hygroscopicity Hygroscopic moisture content of the soil is usually determined by an air-drying method and has been related with the surface area and cation exchange capacity of the soil, by many researchers. However, as relative humidity influences the overall soil-water interaction, quantification of its impact on hygroscopic moisture content of the soil becomes mandatory. There are several types of hygroscopicity. Kuron’s hygroscopicity is used in Hungary.

Density of the soil Density is defined as mass per unit volume. Particle density is the density of only the mineral particles that make up a soil; i.e., it excludes pore space and organic material. Particle density averages approximately 2.65 g/cc (165 lbm/ft3) Bulk density of the soil Soil bulk density of a sample is the ratio of the mass of solids to the total or bulk volume. This total volume includes the volume of both solids and pore space. Calculation of total porosity

Determination of soil porosity Pore space is that part of the bulk volume that is not occupied by either mineral or organic matter but is open space occupied by either air or water. Ideally, the total pore space should be 50% of the soil volume. The air space is needed to supply oxygen to organisms decomposing organic matter, humus, and plant roots. Pore space also allows the movement and storage of water and dissolved nutrients. There are four categories of pores: 1.Very fine pores: < 2 microns 2.Fine pores: 2-20 microns 3.Medium pores: microns 4.Coarse pores: 200 microns-0.2 mm

Water retention Water retention is defined as the soil water content at a given soil water suction. Water is retained in a soil when the adhesive force of attraction of water for soil particles and the cohesive forces water feels for itself are capable of resisting the force of gravity which tends to drain water from the soil. Capillary action in soil Capillary water is held in the capillary pores (micro pores). Capillary water is retained on the soil particles by surface forces. It is held so strongly that gravity cannot remove it from the soil particles. The molecules of capillary water are free and mobile and are present in a liquid state.

4. Chemical properties of soils Chemical reaction (pH) of soils CaCO 3 content of soils Soil acidity Cation exchange capacity (T-value) and extractable cations in soil Total water-solvable salinity Organic matters in soil Characterization of humus quality Mineral nitrogen in soils Well solvable phosphorus content of soils Well solvable potassium content of soils Electrical conductivity of soil

Chemical reaction (pH) of soils pH of soils Soil reactivity is expressed in terms of pH and is a measure of the acidity or alkalinity of the soil. More precisely, it is a measure of hydrogen ion concentration in an aqueous solution and ranges in values from 0 to 14 (acidic to basic) but practically speaking for soils, pH ranges from 3.5 to 9.5, as pH values beyond those extremes are toxic to life forms The pH is important for the pH dependent charge of silicates and organic material, therefore for the cation exchange capacity. NamepH value very acidic- 4,5 acidic4,5 – 5,5 little acidic5,5 – 6,8 neutral6,8 – 7,2 little alkaline7,2 – 8,5 alkaline8,5 – 9,0 very alkalineup to 9,0

CaCO3 content of soils Inorganic carbonate either as calcium (calcite) or magnesium (dolomite) carbonate or mixtures of both, occurs in soil as a result of weathering, or is inherited from the parent material. Most soil of arid and semi-arid regions are calcareous. As with alkaline pH, soils with free CaCO3 tend to have lower availability of P and of some micronutrient cations. Consequently, CaCO3 equivalent is normally determined. CaCO 3 + 2HCl = CaCl 2 +H 2 O + CO 2

Soil acidity Acid soils, by definition, are those with pH below 7.0. The lower the pH, the more acid is the soil. Each unit pH drop indicates ten times more acidity. For example, pH 5.0 has 10 times more acidity than pH 6.0, and 100 times more acidity than pH 7.0. many soils have become acid because of warm temperatures and high rain fall. Cation exchange capacity (T-value) and extractable cations in soil Ion exchange is a reversible process by which one cation or anion held on the solid phase is exchanged with another cation or anion in the liquid phase, and if two solid phases are in contact, ion exchange may also take place between two surfaces. In most agricultural soils, the cation exchange capacity (CEC) is generally considered to be more important than anion exchange (AEC), with the anion molecular retention capacity of these soils usually much smaller than the CEC. Some soils with abundant goethite and gibbsite, as do some oxic horizons or subsoils of Oxisols, may have a CEC to AEC ratio approaching 1.0 (net charge of zero) or a small positive charge.

Total water-solvable salinity Salt-affected soils that are caused by excess accumulation of salts, typically most pronounced at the soil surface. Salts can be transported to the soil surface by capillary transport from a salt laden water table and then accumulate due to evaporation. Organic matters in soil The organic soil matter includes all the dead plant material and all creatures, live and dead. The living component of an acre of soil may include 900 lb of earthworms, 2400 lb of fungi, 1500 lb of bacteria, 133 lb of protozoa and 890 lb of arthropods and algae..

Characterization of humus quality Humus refers to organic matter that has been decomposed by bacteria, fungi, and protozoa to the final point where it is resistant to further breakdown. Humus usually constitutes only five percent of the soil or less by volume, but it is an essential source of nutrients and adds important textural qualities crucial to soil health and plant growth. Mineral nitrogen in soils Nitrogen is the most critical element obtained by plants from the soil and is a bottleneck in plant growth. Plants can use the nitrogen as either the ammonium cation ammonium (NH4+) or the anion nitrate (NO3-).

Well solvable phosphorus content of soils Phosphorus is the second most critical plant nutrient. The soil mineral apatite is the most common mineral source of phosphorus. While there is on average 1000 lb of phosphorus per acre in the soil, it is generally in unavailable forms. Solvable phosphorus content of soils solvable phosphorus content AL- solvable phosphorus content (P 2 O 5 mg/100 g soil) Clay soilLoam soilSand soil very low< 235 low moderately little much much very much>

Well solvable potassium content of soils The amount of potassium in a soil may be as much as 80,000 lb per acre, of which only 150 lb or 2% is available for plant growth. Solvable potassium content of soils Electrical conductivity of soil Soil salinity is generally measured by the electrical conductivity (EC) of a soil extract. solvable potassium content AL- solvable potassium content (K 2 O mg/100 g soil) Soil type SandLoamClay very low< 5< 7< 10 low moderately little much much very much> 26> 31> 36

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